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Title: CUTANEOUS ANTIBODIES FROM CHANNEL CATFISH IMMUNE TO ICHTHYOPHTHIRIUS MULTIFILIIS (ICH) INDUCED APOPTOSIS OF ICH THERONTS

Author
item Xu, Dehai
item Klesius, Phillip
item Shoemaker, Craig

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2005
Publication Date: 4/1/2005
Citation: Xu, D., Klesius, P.H., Shoemaker, C.A. 2005. Cutaneous antibodies from channel catfish immune to ichthyophthirius multifiliis (ich) induced apoptosis of ich theronts. Journal of Fish Diseases 28(4): 213-220.

Interpretive Summary: The infectivity of Ichthyophthirius multifiliis (Ich), a severe fish parasite, was reduced after exposure to antibodies (a protective substances produced by the fish immune system) from fish immune to Ich. The immobilized theronts exhibited high mortality after exposure to either high concentrations of antibody or prolong exposure to low concentrations of antibody. In order to study the immune response of channel catfish against this parasite, it is necessary to understand the effect of antibody on Ich theronts. This study explored the existence of apoptosis (programmed cell death) in Ich and determined the effect of antibodies on theronts apoptosis. The study results demonstrated that the antibodies from fish immune to Ich induced cell death in Ich theronts. The percentage of apoptotic theronts increased with the amount of antibody and the length of exposure time to antibodies. These results are critically important for understanding immune protection of fish and will aid in the success of developing vaccines against the parasite.

Technical Abstract: This study explored the existence of apoptosis (programmed cell death) in protozoan Ichthyophthirius multifiliis (Ich) theronts and determined the effect of cutaneous antibodies in the skin culture fluid from fish immune to Ich on theronts apoptosis. Apoptosis was detected on theronts and was clearly distinguished by fluorescent microscopy after staining with acridine orange and propidium iodide. The apoptotic theronts showed characteristic chromatin condensation and nucleus fragments containing chromatin pieces. The externalization of phosphatidylserine (PS) on the plasma membrane of apoptotic theronts was detected with FITC conjugated annexin using flow cytometry. Theront apoptosis was induced using the skin culture fluid from fish immune to Ich, which contained cutaneous Ich antibodies. The highest apoptosis appeared in theronts exposed to immune skin culture fluid at a 1:10 dilution compared to those at 1:20 and 1:40 dilutions. A direct correlation was noted between the percentage of apoptotic theronts and exposure duration to immune skin culture fluid. The study results demonstrated that the cutaneous antibodies in the immune skin culture fluid induced apoptosis of Ich theronts.